Color stabilized lubricating oil



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Patented Au 3 Md 53 (361L812 STABEHZ EEE LUBRMATENG Gilli. Charles L Thomas, Ewarthmore, Archibald P. Stuart,

Media, and Haber M. Khelghatian, Springfield, Pa, as-

siguors to Sun Oil Company, ilhiladelphia, Pa, a corporation of New Jersey No firawmg'. Filed Apr. 3, 195b, fier. No. 726358 This invention relates to petroleum lubricating oils containing color stabilizing additives.

Various additive materials have been proposed for use in petroleum lubricating oils in order to improve the color stability of such oils. The present invention provides additives which have not previously been employed in lubricating oils and which are remarkably effective for such purpose, providing results which are in general superior to those obtained with prior art additives. In some cases, the use of additives according to the invention actually provides the unusual beneficial result of improving the color of the lubricating oil upon aging. The

additives according to the invention also have a beneficial effect on the cast of the petroleum oil.

The additives according to the invention are beneficially used in petroleum lubricating oils from various types of crude, for example naphthenic crude, parafiinic crude, mixed base crude, etc. The additives comprise hydrazine and certain allcyl and hydroxyalkyl derivatives thereof, and these additives including hydrazine and derivatives will hereinafter be referred to as hydrazine additives.

Hydrazine and derivatives thereof have been employed in the prior art as additives for gasoline, for example as gum inhibitors. However, various of these prior art additives are inoperative to improve the color stability of lubricating oil, and the prior art failed to indicate that certain other hydrazine additives are not only beneficial but remarkably effective for improving the color stability of lubricating oils.

The hydrazine additives according to the invention are those having the formula RNHN(R')R where R is hydrogen, an alkyl radical or a hydroxyalkyl radical, R is hydrogen or an alkyl radical or a hydroxyalkyl radical, and R" is hydrogen or an alkyl radical or a hydroxyalkyl radical. Preferably the alkyl or hydroxyalkyl radicals contain not more than 5 carbon atoms.

Although the hydrazine additives contemplated by the above formula are generally effective in improving the color stability of lubricating oils, they are not all equivalent in certain other respects. For example, trisubstituted hydrazines and symmetrical disubstituted hydrazines diifer from hydrazine itself, from asymmetrical disubstituted hydrazines and from monosubstituted hydrazines, in that the latter hydrazine additives produce haze in lubricating oils upon aging, whereas the former hydrazine additives do not. This haze formation is apparently the result of reactions undergone by the hydrazine additive and constituents of the oil to produce water as a product. It is frequently undesirable that petroleum products develop haze upon aging, and the trisubstituted hydrazines and the symmetrical disubstituted hydrazines are preferred additives for use in instances where haze formation is undesirable.

A preferred hydrazine additive for use according to the invention is a trihydroxyalkyl hydrazine, and more preferably tris(2-hydroxypropyl) hydrazine. These additives provide good color stability in the lubricating oil without haze formation, and they have the further advantage that they can be readily prepared by reaction of an alkylene oxide with hydrazine. In the latter respect, they have an advantage over symmetrical disubstituted hydrazines, which cannot satisfactorily be prepared by reaction of alkylene oxide with hydrazine, since such reaction results to an undesirable extent in the asymmetrical rather than the symmetrical disubstituted hydrazine.

The additives according to the invention can be employed for example in amounts of 0.005 to 1 weight percent of the lubricating oil, though usually it is preferred not to employ more than 0.5 weight percent. The solubi ity of the additive in lubricating oil varies with the structure of the additive. Generally, greater numbers of carbon atoms in the molecule contribute to hydrocarbon solubility, whereas the presence of hydroXyl radicals in the molecule generally-detracts from the solubility in lubricating oil. A person skilled in the art can in the light of the present specification readily determine suitable amounts of additive for use in a given instance.

The additives according to the invention can be employed together with other known additives for improving the oxidation stability, corrosion resistance, extreme pressure properties, etc. of lubricating oils. It is preferred, however, that the additive not be employed with acidic additives which would tend to neutralize the basic nitrogen atoms of the hydrazine additive.

The hydrazine additives employed according to the invention can also be used as treating agents to improve the color stability of petroleum lubricating oils, as dis closed and claimed in copending application Serial No. 559,725. Such use as treating agent involves removal of excess hydrazine material, if any, and of reaction products of the hydrazine material with constituents of the lubricating oil, such removal being preferably performed directly after the treating. In the use of the materials as additives, on the other hand, there is no such separation, and the additive is allowed to remain in the lubricating oil during subsequent storage, transportation, use, etc. The treating technique may be beneficial in instances where a hydrazine material, which would otherwise result in haze formation, is employed, the water which is formed in the treating being removed after the treating together with excess of the hydrazine material. Generally, in such operation, haze is not formed subsequently in the lubricating oil.

If desired, the hydrazine material can be employed as a treating agent together with an alkaline treating agent such as caustic soda. The use of the hydrazine material in this manner results in improved color stability of the treated oil as compared with oil treated with caustic soda alone.

In treating operations generally, the temperature is usually within the approximate range from room temperature to 650 F., and preferably in the range from 150 to 450 F. The hydrazine material employed can be either in liquid or vapor phase, though liquid phase operation is preferred. Elevated pressure can be employed if necessary to maintain the hydrazine material in liquid phase. The amount of the hydrazine material employed can either be less than the maximum amount which is soluble in the lubricating oil, or it can be a greater amount, for example up to an equal volume.

The following examples illustrate the invention:

Various hydrazine additives were employed in 0.05 weight percent concentration in a naphthenic lubricating oil distillate having Saybolt Universal viscosity at F. of about 700 seconds. The oil containing the additive was aged in each instance in a closed system for 16 hours at 229 F. For purpose of comparison, the same oil containing no additive was also aged under the same conditions. The color of the lubricating oil was determined by optical density measurement (absorbance at 525 millimicrons multiplied by a factor of 100). For each additive, an improvement factor was determined by subtracting the OD. color of the initial oil from the color of the aged oil with additive, and dividing this difierence by the spa-s,

diiierence between the colors of the aged oil without additive and the initial oil, multiplying the division product by 100 and subtracting the resulting figure from 100. An improvement factor of 100 as determined in this manner, indicates an oil which does not change color upon aging, while an improvement factor of zero indicates an oil which is degraded in color upon aging to the same extent as the oil without additive.

The following table shows the results obtained with various hydrazine additives according to the invention:

Optical Density Color Additive Aged Aged Improve- Initial with without merit Additive Additive Factor Symmetrical dimethyl hy drazine 10.5 9. 4. 18. 4 114 Monomethyl hydrazine 10.5 9.5 18.4 113 Monohydroxyethyl hydrazine 9. 8 9. 6 18.1 102 4% Aqueous hydrazine 10. 10. 5 18.4 100 Trimethyl hydrazine 10. 5 12. 4 18. 4 76 Tris (2 hydroxypr yl hydrazine 9. 9 12. 5 18. 2 69 Asymmetrical dimethyl hydrazine 10. 5 14. 6 18. 4 48 Trihydroxyethyl hydrazine" 10.2 15.0 18.2 40

Of the above additives according to the invention, symmetrical dimethyl hydrazine, tris(2-hydroxypropyl) hydrazine, trimethyl hydrazine and trihydroxyethyl hydrazine produced no haze in the lubricating oil during the aging period, whereas the other additives did.

The tris(2-hydroxypropyl) hydrazine was prepared by stirring anhydrous hydrazine in a nitrogen atmosphere at 75 C. and adding propylene oxide slowly. In the initial stages the reaction was quite exothermic. Three moles of propylene oxide were employed per mole of hydrazine. While the last of the epoxide was being added, the temper- It is within the scope of the invention, when employing reaction products of alkylene oxides with hydrazines as additives or treating agents, to prepare the reaction products in situ in the lubricating oil. In such operation, the hydrazine and the alkylene oxide are added to the lubricating oil and reacted therein to form the hydroxyalkyl derivative.

It is essential according to the invention that the hydrazine additive contain at least one hydrogen atom connected to a nitrogen atom. Tetramethyl hydrazine for example is inefifective to improve the color stability of lubricating oil.

In one embodiment of the invention, the hydrazine additive or treating agent contains water. Thus, for example, 54% aqueous hydrazine has been shown to provide particularly good color stabilization. In some instances at least, superior results are obtained with aqueous materials as compared wth anhydrous materials.

The present application is a continuation-in-part of application Serial No. 559,725, tilted January 17, 1956, and now US. Patent 2,975,136, which discloses and claims certain processes for treating hydrocarbon materials with hydrazine and derivatives thereof and certain compositions comprising petroleum fractions and aqueous hydrazine or derivatives.

The invention claimed is:

1. A new composition of matter consisting essentially of a petroleum lubricating oil and 0.005 to 1 weight percent of a material having the formula RNI-IN(R)R Where R, R and R are each selected from the group consisting of hydrogen, alkyl radicals having not more than 5 carbon atoms and hydroxyalkyl radicals having not more than 5 carbon atoms.

ature was raised to about 100 C. and maintained there for about 30 minutes. The crude reaction product was distilled to obtained as distillate the material employed as the additive.

The preparation of the trihydroxyethyl hydrazine was generally similar except that ethylene oxide was used, and the crude reaction product was employed as additive without distillation.

The preparation of the monohydroxyethyl hydrazine was generally similar except that one mole of ethylene oxide was employed per mole of hydrazine and the temperature was maintained at about 75 C. throughout the reaction.

For purpose of comparison, various hydrazine derivatives which are not within the scope of the invention were tested in a similar manner as that described previously. The following results were obtained:

' This table shows that various materials which are disclosed in the prior art as gum inhibiting or antioxidant additives, etc. for gasoline are ineffective as color stabilizing additives for petroleum lubricating oils.

2. The lubricating oil composition according to claim 1 wherein said material is a tris(hydroxyalkyl) hydrazine.

3. The lubricating oil composition according to claim 1 wherein said material is a symmetrical diallcyl hydrazine.

4. The lubricating oil composition according to claim 1 wherein said material is symmetrical dimethyl hydrazine.

5. The lubricating oil composition according to claim 1 wherein said material is a trialkyl hydrazine.

6. The lubricating oil composition according to claim 1 wherein said material is trimethyl hydrazine.

7. The lubricating oil composition according to claim 1 wherein said material is hydrazine.

8. The lubricating oil composition according to claim 1 wherein said material is tris(2-hydroxypropyl) hydrazine.

9. The lubricating oil composition according to claim 1 wherein said material is monomethyl hydrazine.

References Qited in the file of this patent UNITED STATES PATENTS 1,906,044 Burk Apr. 25, 1933 2,027,394 McMullen Jan. 14, 1936 2,729,690 Oldenburg Jan. 3, 1956 2,966,462 Spindt et a1 Dec. 27, 1960 FOREIGN PATENTS 423,938 Great Britain Feb. 11, 1935 OTHER REFERENCES Practice of Lubrication, by Thomsen, 4th ed. (1951), p. 51, pub. by McGraw-Hill Book Co.

The Chemistry of Hydrazine, by Andrieth et al.

(1951), pp. 225-227, pub. by John Wiley & Sons. 

1. A NEW COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A PETROLEUM LUBRICATING OIL AND 0.005 TO 1 WEIGHT PERCENT OF A MATERIAL HAVING THE FORMULA RNHN(R'')R" WHERE R, R'' AND R" ARE EACH SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL RADICALS HAVING NOT MORE THAN 5 CARBON ATOMS AND HYDROXYALKYL RADICALS HAVING NOT MORE THAN 5 CARBON ATOMS. 